The invention relates to a high frequency surgical instrument and in particular to high frequency surgical instruments which are intended for the coagulation of biological tissue with high frequency energy.
In the coagulation of biological tissue with high frequency energy the tissue is heated as a result of the current flow and the blood stoppage is achieved through a complex thermally activated biochemical action mechanism. This process rests mainly on the thermal conversion of the proteins in the blood from about 60.degree. C. onwards and from the blood coagulation. Disadvantageous in this is that tissue and blood stick to the coagulation electrodes, through which the vessel in the biological tissue which had just been closed can tear open again and the current flow for the next coagulation can be hindered through the resistance increase. This sticking is influenced by a plurality of factors; the greater the electrode heating is, the stronger is the sticking.
From the book "Hochfrequenz-und Lasertechnik in der Medizin" by Reidenbach, Springer Verlag, 1983, pages 148 to 167, a method of hydrothermozation is already known in which distilled water or a saline solution emerges from bores of hollow coagulation electrodes and the sticking effect is reduced through the cooling action and/or the separation of electrode and tissue which thereby sets in. Disadvantageous in this known method is on the one hand the non-uniformity of the liquid output in the region of the treatment electrode and/or the large amount of liquid which is required for a salt jet HF coagulation and which inevitably makes the coagulation itself more difficult through its cooling action.
This principle was already used for the flushing of a bipolar coagulation forceps (DE-OS 44 40 158). Disadvantageous in this is that here as well the uniformity of the liquid output is insufficient and the flushing liquid cannot emerge between the tissue and branches of the forceps during the coagulation.
From DE-PS 42 12 053 it is known to provide a hard material layer on the electrodes, which however has only an insufficient effectiveness since the electrical impedance of the electrodes is increased and thereby higher electrical voltages are given off by the high frequency generator, which again reinforce the sticking. Anti-adhesion layers on a Teflon basis or silicon coatings (U.S. Pat No. 5,549,604) act similarly disadvantageously.